8 February 2008, Computational Social Choice Seminar, Jérôme Lang

Abstract:
In many real-world group decision making problems, the set of alternatives is a Cartesian product of finite value domains for each of a given set of variables (or issues). Dealing with such domains leads to the following well-known dilemma: either ask the voters to vote separately on each issue, which may lead to so-called multiple election paradoxes as soon as voters' preferences are not separable; or allow voters to express their full preferences on the set of all combinations of values, which is practically impossible as soon as the number of issues and/or the size of the domains are more than a few units. We try to reconcile both views and find a middle way, by relaxing the extremely demanding separability restriction into this much more reasonable one: there exists a linear order x_1 > ... > x_p on the set of issues such that for each voter, every issue x_i is preferentially independent of x_{i+1},..., x_p given x_1,..., x_{i-1}.

This leads us to define a family of sequential voting rules, defined as the sequential composition of local voting rules. These rules relate to the setting of conditional preference networks (CP-nets) recently developed in the Artificial Intelligence literature. Lastly, we study in detail how these sequential rules inherit, or do not inherit, the properties of their local components.

This is joint work with Lirong Xia.

For more information, see http://www.illc.uva.nl/~ulle/seminar/, or contact Ulle Endriss (ulle at illc.uva.nl).